/*
 * Licensed to CRATE Technology GmbH ("Crate") under one or more contributor
 * license agreements.  See the NOTICE file distributed with this work for
 * additional information regarding copyright ownership.  Crate licenses
 * this file to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.  You may
 * obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * However, if you have executed another commercial license agreement
 * with Crate these terms will supersede the license and you may use the
 * software solely pursuant to the terms of the relevant commercial agreement.
 */

package io.crate.metadata;

import org.apache.lucene.util.BytesRef;
import org.elasticsearch.common.lucene.BytesRefs;

import java.util.function.Function;

public abstract class RowContextCollectorExpression<TRow, TReturnValue> implements RowCollectExpression<TRow, TReturnValue> {

    protected TRow row;

    @Override
    public void setNextRow(TRow row) {
        this.row = row;
    }

    public static <TRow, TReturnValue> RowCollectExpression<TRow, TReturnValue> forFunction(Function<TRow, TReturnValue> fun) {
        return new FuncExpression<>(fun);
    }

    public static <TRow> RowCollectExpression<TRow, BytesRef> objToBytesRef(Function<TRow, Object> fun) {
        return forFunction(fun.andThen(BytesRefs::toBytesRef));
    }

    private static class FuncExpression<TRow, TReturnVal> extends RowContextCollectorExpression<TRow, TReturnVal> {

        private final Function<TRow, TReturnVal> f;

        FuncExpression(Function<TRow, TReturnVal> f) {
            this.f = f;
        }

        @Override
        public TReturnVal value() {
            return f.apply(row);
        }
    }
}
